DESERT SAND-DUNES 49 



of an elevated, undulating plain pitted with hollows . 

 The profile of each pit in the direction of the wind 

 was the same as that of the regular waves, except 

 that some of the lower parts of the sand-wave 

 were wanting, all the sand being removed, leaving 

 a floor of hard material. The floor of the pit was 

 in some cases oval in shape ; in others loose sand 

 lay within the oval on the lee side, making the 

 floor crescentic in form, recalling the shape of a 

 horse's footprint. There remained, however, the 

 characteristic steep slope on one side and gentle 

 slope on the other. Pits of this shape and of great 

 depth were observed by Mr. W. S. Blunt ^ in the 

 Arabian Nefud, where they are called fuljes. 

 It has taxed the ingenuity of more than one writer 

 to imagine a mode of action by which the wind 

 could scour out holes of such a great depth and 

 of this peculiar and constant form. I have not 

 seen the large structures described by Mr. W. S. 

 Blunt, but wherever they are formed in loose sand 

 I believe that they are what I saw on the Helwan 

 sandbanks. The weather and lee sides of the pit 

 are not parts of one structure, but the lee and 

 weather slopes respectively of two succeeding sand- 

 waves. In a later part of this work I shall describe 

 how I observed pits of similar shape left at low 

 ' Appendix to "A Pilgrimage to Nejed." 



